Method and device for the continuous casting of killed steel with artificial wildness

ABSTRACT

The invention has for its object a method and device for the continuous casting of killed steel with artificial wildness.

United States Patent 1191 Di Candia I METHOD AND DEVICE FOR THECONTINUOUS CASTING OF KILLED STEEL WITH ARTIFICIAL WILDNESS [75]Inventor: Armando Di Candia, Genoa, Italy [73] Assigncc: ItalsiderS.p.A., Genoa. Italy {22 Filed: June 4, I973 [211 Appl. No.: 366,428

[30] Foreign Application Priority Data June 6, 1972 Italy 12706/72 Aug.22, 1972 Italy 12857/72 [52] US. Cl 164/66; 164/281 [51] Int. Cl. B22D11/10 [58] Field of Search 164/66, 134, 259, 281

[56] References Cited UNITED STATES PATENTS 3.208.117 9/1965 Goedecke et:11 164/134 X 1451 Sept. 30, 1975 6/1970 M1115 et al. Q. 164/134 x12/1973 Paton et a1 164/52 FOREIGN PATENTS OR APPLICATIONS 3,816,6099/1963 Japan 164/66 1,916,919 10/1970 Germany ..164/66 PrimaryE.\'aminerFrancis S. Husar Assistant Examiner-John E. Roethel Attorney,Agent, or I-irmWolfgang G. Fasse; Willard W. Roberts 5 7 ABSTRACT Theinvention has for its object a method and device for the continuouscasting of killed steel with artificial wildness.

4 Claims, 6 Drawing Figures METHOD AND DEVICE FOR THE CONTINUOUS CASTINGOF KILLED STEEL WITH ARTIFICIAL WILDNESS BACKGROUND OF THE INVENTION Itis known that in a continuous casting of killed steel the non-metallicinclusions. caused by the erosions of the refractories, by the chemicalreactions occurring in the metallurgic processes of manufacture.treatment and solidification, by the oxidation caused by theatmospherical agents (particularly if aluminium in the metal phase ispresent in the steel) are often the reason of the superficial defectsappearing on the surface of sheet material made of the products of saidcontinuous casting.

It was particularly shown that, as the relevant technical literatureteaches, said superficial defects are often caused by the non-metallicinclusions which, during the continuous casting, are imprisoned withinthe first portions of steel which hardens in contact with the cooledwalls of the ingot mould. Failing particular devices avoiding the abovementioned disadvantages, the products of the continuous casting whichare to be used in the manufacture of formed sheet material, where saidsuperficial defects are more dangerous, are usually subjected tooperations of total flooding, performed by hand or through suitabledevices, so as to remove said superficial defects.

OBJECT OF THE INVENTION In view of the foregoing, the present inventionaims at removing the disadvantages set forth above.

SUMMARY OF THE INVENTION According to the method of the invention forthe continuous casting of killed steel, in the upper zone of the ingotmould an artificial wildness is caused by blowing an inert bath underthe gas surface.

Said blowing of an inert gas, preferably consisting of argon, under thebath surface is obtained through at least a submerged head lancearranged so that the blowing gas may be directed toward the steel wallwhich is hardening, so as to convey the steel flow in the same directionand remove said dangerous inclusions by making them float on the bathsurface wherefrom they may be easily removed.

A device suitable to embody the above method, of the kind comprising aningot mould for the continuous casting and includes at least a lance forblowing an inert gas under the bath surface, whose nozzles are arrangedso as to direct the interface between the steel flow towards the steelwhich is hardening and the still liquid steel.

In order to form an efficient gas stream within the upper zone of theingot mould, according to a variation of the invention, it is suggestedto increase the number of the outflow ports for said inert gas. Where itis not possible to increase the number of the lances extending fromabove into the liquid bath surface, the solution found was to feed saidinert gas through a plurality of conduits formed in the thickness of theingot mould wall. The conduits may be of copper or other materials.

A device suitable to embody such a variation comprises an ingot mouldfor the continuous casting which includes. at least through its longwalls, a series of passages suitable to feed an inert gas underpressure, under the bath surface.

According to a particular embodiment ofsaid device. said passagespassing through the wall of the ingot mould for the continuous casting.have their inner end. i.e.. the one directed towards the ingot mould.inclined upwards. and further have a preferablycircular cross section.

Further. said passages. according to a modified embodiment, have aslot-like elongated section. with its larger size horizontal, verticalor inclined.

According to a particular embodiment, said passages are obtained throughthe use of porous materials suitably provided on the copper ingot mould.

Finally. the above passages passing through the ingot mould wall have avariable cross section along the thickness of said ingot mould.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may beclearly understood it will now be described, by way of example only.with reference to the accompanying drawings. wherein:

FIG. 1 is a diagrammatic vertical section, along line [-1 of FIG. 2 ofan ingot mould for the continuous casting, provided with the devicesuitable to embody the claimed method;

FIG. 2 is a plan view of the ingot mould shown in FIG. 1;

FIG. 3 is a horizontal cross section of an ingot mould for thecontinuous casting, improved according to the invention;

FIG. 4 is a vertical cross section of said ingot mould along line IVIVof FIG. 3; and

FIGS. 5 and 6 show an embodiment having an ingot mold with porous sidewalls.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With particular reference toFIGS. 1 and 2, the steel coming from a suitable container (not shown) isled to a discharger I and. through its outlet ports 2, is fed in to aningot mold 3. The outlet ports 2 may be arranged at different angleswith respect to the discharger axis, and also according to the width ofthe product to be cast.

The steel coming from said discharger is hit by a blow of inert gasblown through one or tubular lances 4. whose position is shown in thefigures by way of example only, arranged so as to cause a motion in thesteel in the upper part of said ingot mould, in order to achieve theinvention object.

Through the injection of an inert gas, preferably argon, a controlledturbulence is obtained and an agitation in the upper part of said ingotmould along whose perimeter is formed a substantially continuous wave 5.Said motion prevents the non-metallic material from concentrating on theinterface between the steel which is hardening and the still liquidsteel. Further, said motion, owing to the continuous washing of thesurface of the hardening steel. decreases the tendency of thenonmetallic inclusions to be imprisoned therein. Said motion is similarto the one obtained during the treatment of wild steel cast in thetraditional ingot mould.

With particular reference to FIGS. 3 and 4: the steel coming from asuitable container (not shown) passes through a discharger 101 and,through its outlet ports. is conveyed into an ingot mould 103; accordingto the embodiment shown in FIGS. 1 and 2, said outlet ports may bearranged according to different angles with respect to the dischargeraxis and according to the width of said ingot mould.

According to a modified embodiment, said discharger may be omitted, insuch a case. the molten metal coming from said suitable basket isdischarged directly into the ingot mould.

The steel poured into said ingot mould is hit by the blows ofinert gascoming from conduits 104, whose position is shown in the figures by wayof example only. which may be obtained through the use of porousmaterials suitably provided on said ingot mould.

Said conduits are arranged in the ingot mould wall so i as to cause amotion in the molten steel in the upper part of said ingot mould; saidmotions in the molten steel have the purpose of carrying, together withthe stream of neutral gas. the possible inclusions towards the bathsurface. preventing them from being imprisoned within the steel layerwhich is getting hard on the lower parts of the inner wall of said ingotmould.

Through the injection of an inert gas, a controlled turbulence and anagitation are obtained in the upper part of said ingot mould, therefore.a substantially continuous wave 105 is formed along the perimeter ofsaid ingot mould.

Such a motion prevents the non-metallic material from concentrating atthe interface between the hardening steel and the still liquid steel.Further. said motion owing to the continuous washing of the surface ofthe steel getting hard, decreases the tendency of the inclusions to beimprisoned therein. Such a motion is similar to the one obtained duringthe treatment of the wild steel cast in the traditional ingot moulds.

The conduits 104, passing through the ingot mould wall, are preferablyinclined upwards so as to facilitate streams of liquid metal tending toform a peripheral continuous wave 105.

The cross section of said nozzles may be constant or variable within thethickness of the ingot mould wall, according to principles known per se,for obtaining in each case. the best efficiency of the gaseous blowentering the fluid metal. Said gas may be also made to pass throughporous materials suitably provided on the copper ingot mould.

Conduits 104 may be provided also only in the long walls of said ingotmould. In the same way. said conduits 104 may be in the form of ahorizontal, vertical or inclined slot.

FIG. 5 shows a mold similar to FIG. 4, however. the conduits 104 for theinert gas have been replaced by mold walls which are sufficiently porousto permit the inert gas to travel through the walls. FIG. 6 shows aporous wall portion of a mold on an enlarged scale.

It is to be understood that the invention is not limited to the examplesshown. It is intended to cover all modifications and equivalents withinthe scope of the appended claims.

What we claim is:

1. In a method for the continuous casting of killed steel into a mold bymeans of a tubular member reaching downwardly into the mold. wherein aninert gas is blown into the mold simultaneously with the molten steel,the improvement comprising blowing said inert gas into the top portionof the ingot being east through the mold side walls just under the topsurface of the ingot being cast and above the layer of steel hardeningon the inner surface of the mold walls so that a continuous wave isformed and sustained in said top surface of the ingot being cast, saidcontinuous wave washing impurities in the molten steel to the surface ofthe ingot being cast to thus prevent the concentration of impurities atthe interface between the hardening steel and the still liquid steel.

2. In an apparatus for the continuous casting of killed steel into amold having elongated side walls and short side walls, and a meltdischarging nozzle closed at its lower end and reaching downwardly intothe mold substantially intermediate said short mold side walls, saidmelt discharging nozzle having two substantially horizontally directedmelt discharging openings adjacent to said lower end of said nozzle,each of said melt discharging openings facing its respective short sidewall. the improvement comprising means in said side walls of the moldfor injecting an inert gas into the molten metal just under the topsurface of the ingot being cast, and above the layer of steel hardeningon the inner surface of the mold walls for creating a continuous wave inthe surface of an ingot being cast, whereby impurities are continuouslywashed to the surface and thus prevented from concentrating at theinterface between the hardening steel and the still liquid steel.

3. The apparatus according to claim 2, wherein said means for injectingan inert gas comprise conduits extending through said side walls. saidconduits being upwardly inclined.

4. The apparatus according to claim 2, wherein said means for injectingan inert gas comprise porous ingot side wall portions at the upper endthereof.

1. In a method for the continuous casting of killed steel into a mold bymeans of a tubular member reaching downwardly into the mold, wherein aninert gas is blown into the mold simultaneously with the molten steel,the improvement comprising blowing said inert gas into the top portionof the ingot being cast through the mold side walls just under the topsurface of the ingot being cast and above the layer of steel hardeningon the inner surface of the mold walls so that a continuous wave isformed and sustained in said top surface of the ingot being cast, saidcontinuous wave washing impurities in the molten steel to the surface ofthe ingot being cast to thus prevent the concentration of impurities atthe interface between the hardening steel and the still liquid steel. 2.In an apparatus for the continuous casting of killed steel into a moldhaving elongated side walls and short side walls, and a melt dischargingnozzle closed at its lower end and reaching downwardly into the moldsubstantially intermediate said short mold side walls, said meltdischarging nozzle having two substantially horizontally directed meltdischarging openings adjacent to said lower end of said nozzle, each ofsaid melt discharging openings facing its respective short side wall,the improvement comprising means in said side walls of the mold forinjecting an inert gas into the molten metal just under the top surfaceof the ingot being cast, and above the layer of steel hardening on theinner surface of the mold walls for creating a continuous wave in thesurface of an ingot being cast, whereby impurities are continuouslywashed to the surface and thus prevented from concentrating at theinterface between the hardening steel and the still liquid steel.
 3. Theapparatus according to claim 2, wherein said means for injecting aninert gas comprise conduits extending through said side walls, saidconduits being upwardly inclined.
 4. The apparatus according to claim 2,wherein said means for injecting an inert gas comprise porous ingot sidewall portions at the upper end thereof.